1. Field of the Invention
The present invention relates to a peripheral or side channel feed pump with a driven impeller which rotates in a casing and in which guide vanes delimiting a ring of vane chambers is arranged, wherein the casing includes part-annular channels arranged therein proximate the guide vanes to form with the vane chambers a feed chamber for feeding a liquid from an inlet duct to an outlet duct, the vane chambers passing through the impeller and including at least two sectors or areas connected to one another, each sector being contiguous to at least one end face of the guide vanes.
2. Description of the Related Art
Peripheral or side channel feed pumps are used, for example, in present-day motor vehicles for feeding fuel or washing liquid. These feed pumps often have the flow passing through them axially and therefore have a particularly compact design. The impeller of the known feed pump has a nonround recess which passes straight through the impeller and is slipped onto an electric motor shaft designed in conformity to the recess. The geometry of the vane chambers may be configured to adapt the feed pump to an intended characteristic curve and to the viscosity of the liquid to be fed. This adaption is critical for the efficiency of the feed pump in the intended application. V-shaped guide vanes are often used in axial-throughflow feed pumps. Sectors of the vane chambers extend from the end face of the impeller as far as the region where the guide vanes are angled. The impeller is manufactured or sintered mostly from plastic by the injection molding method.
A disadvantage of the known feed pump is that the impeller is difficult to manufacture. Halves of a mold such as, for example, an injection mold, a transfer mold, or a sintering mold are in each, case provided with projections designed in conformity to the sectors of the guide chambers to be produced between the guide vanes. To remove the impeller from the mold, the halves have to be rotated simultaneously and drawn apart from one another because of the V-shaped configuration of the guide vanes. Furthermore, a core with a central recess requires a separate manufacturing step because the central recess is oriented perpendicularly to the end faces of the impeller. The above factors lead to a highly cost-intensive manufacture of the impeller.
A proposed solution comprises leading the vane chambers straight through the impeller. As a result, the impeller can easily be manufactured in an axial-removal mold. However, the feed pump provided with such an impeller has particularly low efficiency.
An object of the present invention is to provide a peripheral or side-channel feed pump that may be configured in a large number of applications and that has an impeller that can be manufactured as simply as possible.
The object is met, according to an embodiment of the present invention, by an impeller comprising two opposing axial end faces and a plurality of guide vanes arranged in circumferential succession. Each adjacent pair of guide vanes defines a vane chamber therebetween which comprises two sectors. At least one of the sectors facing one of the end faces of the impeller is designed in an undercut-free arrangement relative to a direction perpendicular to this end face.
The undercut-free design of the sectors allows the impeller to be removed from an injection mold in one simple step when the projections of two mold halves are designed in the shape of the sectors. Mold parts for forming the undercut-free sectors may therefore be manufactured in one piece for forming both the guide vanes and a core having a central recess. Consequently, a separate manufacturing step for forming the core is not required for producing the impeller by injection molding, transfer, or sintering. The impeller can thus be manufactured in a particularly simple and cost-effective way. By a suitable design of the sectors, the feed pump may be configured for use in a wide variety of applications as a result of a suitable choice in the geometry of the vane chambers.
According to an advantageous development of the invention, the formation of burrs between the two sectors may be largely avoided if the vane chambers lead straight through the impeller over their entire height in at least one narrow region. This design allows the mold parts of the impeller to be brought reliably into a position during the production of the impeller in which they rest against one another without a gap. Furthermore, a burr which does form between the mold parts in the vane chambers is thereby located in a central portion of the vane chamber between two vane guides and points in radial directions of the impeller. Consequently any burrs which may possibly form are arranged in a region located outside the guide vanes. A possible burr therefore leads merely to insignificant flow losses within the vane chambers.
The feed pump according to the present invention has particularly high efficiency when one of the sectors comprises an inlet region of the impeller and is in the form of a nozzle and the opposite sector comprises an outlet region of the impeller and is in the form of a diffuser. Alternatively, the sectors may in each case have parts both of the diffuser and of the nozzle in their regions contiguous to one another.
A further increase in the efficiency of the feed pump according to the present invention may be achieved when a tangential section of each guide vane has an L-shaped design.
According to another advantageous embodiment of the present invention, the flow fed into the outlet-side part-annular channel experiences particularly high acceleration in the vane chambers when the outlet-side leg of the guide vanes is arranged approximately perpendicularly to the end face of the impeller. The feed pump according to the invention may thereby generate a particularly high pressure.
According to another advantageous embodiment of the present invention, turbulences of the flow to be fed are kept particularly low when the free end of the inlet-side leg of the L-shaped guide vane is rounded. As a result the feed pump according to the invention may be suitable particularly for use as a fuel pump, since hot fuel tends to evaporate in the active turbulences. Such evaporation leads to a sharp drop in the efficiency of the feed pump.
A uniform and turbulence-free acceleration of the flow within the vane chambers may be ensured in a simple way when the guide vane contour facing away from the direction of movement to the impeller has an essentially uniform radius of curvature. As a result, the contour pointing in the direction of movement can be adapted for the intended characteristic curve and for the respective application of the feed pump.
Turbulences during the transition of the flow from the vane chambers into the outlet-side part-annular channel may be avoided in a simple way when the contour of the outlet-side region of the guide vanes is oriented so as to point opposite to the direction of movement of the impeller.
According to a further embodiment of the present invention, a particularly high pressure of the fed medium may be achieved when the outlet duct is configured as a diffuser.